The present invention relates to an image transferring device for use in image forming equipment which prevents an image from being omitted in a trailing edge portion of a paper sheet despite the application of pre-transfer discharge to a photoconductive element prior to image transfer.
In an electrophotographic copier or similar image forming equipment using an electrophotographic procedure, it often occurs that a reproduction of a solid image has an irregular density distribution in the form of spots. To eliminate such an occurence, it has been customary to provide a pre-transfer lamp or similar pre-transfer discharger between a developing device and an image transfer station. The pre-transfer discharger discharges a photoconductive element prior to image transfer and thereby enhances efficient image transfer. Discharging the photoconductive element in advance at the image transferring stage, however, brings about a problem that a trailing edge portion of a paper sheet where an image should exist is apt to remain simply blank. Specifically, since the pre-transfer discharge increases the difference between the charge on the photoconductive element and the charge to be deposited on the paper sheet, even a slight vibration causes a discharge to occur at the image transfer station due to separation. As a result, the charge deposited on the paper sheet leaks to weaken the electrostatic attraction acting between the paper sheet and a toner, resulting in the omission of an image in the trailing edge portion of the paper sheet. While some efforts for eliminating the omission of an image discussed above have been reported, none of them is fully satisfactory.